Revert "Remove RTPVideoHeader::h264() accessors."

This reverts commit dfbced6504720d2c0807d7b92798eb80ba3f8be9.

Reason for revert: Crashes when making a video call.

#9	0x00000001043dd8d8 in webrtc::RTPVideoHeaderH264& absl::variant_internal::TypedThrowBadVariantAccess<webrtc::RTPVideoHeaderH264&>() at /third_party/absl/types/internal/variant.h:315
#10	0x00000001043dd8ac in absl::variant_internal::VariantAccessResultImpl<2ul, absl::variant<webrtc::RTPVideoHeaderVP8, webrtc::RTPVideoHeaderVP9, webrtc::RTPVideoHeaderH264>&&&>::type absl::variant_internal::VariantCoreAccess::CheckedAccess<2ul, absl::variant<webrtc::RTPVideoHeaderVP8, webrtc::RTPVideoHeaderVP9, webrtc::RTPVideoHeaderH264>&>(absl::variant<webrtc::RTPVideoHeaderVP8, webrtc::RTPVideoHeaderVP9, webrtc::RTPVideoHeaderH264>&&&) at /third_party/absl/types/internal/variant.h:597
#11	0x00000001043db778 in webrtc::RTPVideoHeaderH264& absl::get<webrtc::RTPVideoHeaderH264, webrtc::RTPVideoHeaderVP8, webrtc::RTPVideoHeaderVP9, webrtc::RTPVideoHeaderH264>(absl::variant<webrtc::RTPVideoHeaderVP8, webrtc::RTPVideoHeaderVP9, webrtc::RTPVideoHeaderH264>&) at /third_party/absl/types/variant.h:299
#12	0x0000000104558bcc in webrtc::RtpPacketizer::Create(webrtc::VideoCodecType, unsigned long, unsigned long, webrtc::RTPVideoHeader const*, webrtc::FrameType) at webrtc/modules/rtp_rtcp/source/rtp_format.cc:30

Original change's description:
> Remove RTPVideoHeader::h264() accessors.
>
> Bug: none
> Change-Id: I043bcaf358575688b223bc3631506e148b47fd58
> Reviewed-on: https://webrtc-review.googlesource.com/88220
> Reviewed-by: Stefan Holmer <stefan@webrtc.org>
> Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
> Commit-Queue: Philip Eliasson <philipel@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#23971}

TBR=danilchap@webrtc.org,stefan@webrtc.org,philipel@webrtc.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: none
Change-Id: If99bcabdfe3cae7094f24e407bbe2f47233e46e3
Reviewed-on: https://webrtc-review.googlesource.com/88820
Commit-Queue: JT Teh <jtteh@webrtc.org>
Reviewed-by: Zeke Chin <tkchin@webrtc.org>
Reviewed-by: JT Teh <jtteh@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23993}
diff --git a/modules/video_coding/jitter_buffer_unittest.cc b/modules/video_coding/jitter_buffer_unittest.cc
index 756dc52..adb495d 100644
--- a/modules/video_coding/jitter_buffer_unittest.cc
+++ b/modules/video_coding/jitter_buffer_unittest.cc
@@ -1155,19 +1155,17 @@
 TEST_F(TestBasicJitterBuffer, SpsAndPpsHandling) {
   jitter_buffer_->SetDecodeErrorMode(kNoErrors);
 
-  auto& h264_header =
-      packet_->video_header.video_type_header.emplace<RTPVideoHeaderH264>();
   packet_->timestamp = timestamp_;
   packet_->frameType = kVideoFrameKey;
   packet_->is_first_packet_in_frame = true;
   packet_->markerBit = true;
   packet_->codec = kVideoCodecH264;
   packet_->video_header.codec = kVideoCodecH264;
-  h264_header.nalu_type = H264::NaluType::kIdr;
-  h264_header.nalus[0].type = H264::NaluType::kIdr;
-  h264_header.nalus[0].sps_id = -1;
-  h264_header.nalus[0].pps_id = 0;
-  h264_header.nalus_length = 1;
+  packet_->video_header.h264().nalu_type = H264::NaluType::kIdr;
+  packet_->video_header.h264().nalus[0].type = H264::NaluType::kIdr;
+  packet_->video_header.h264().nalus[0].sps_id = -1;
+  packet_->video_header.h264().nalus[0].pps_id = 0;
+  packet_->video_header.h264().nalus_length = 1;
   bool retransmitted = false;
   EXPECT_EQ(kCompleteSession,
             jitter_buffer_->InsertPacket(*packet_, &retransmitted));
@@ -1183,14 +1181,14 @@
   packet_->markerBit = false;
   packet_->codec = kVideoCodecH264;
   packet_->video_header.codec = kVideoCodecH264;
-  h264_header.nalu_type = H264::NaluType::kStapA;
-  h264_header.nalus[0].type = H264::NaluType::kSps;
-  h264_header.nalus[0].sps_id = 0;
-  h264_header.nalus[0].pps_id = -1;
-  h264_header.nalus[1].type = H264::NaluType::kPps;
-  h264_header.nalus[1].sps_id = 0;
-  h264_header.nalus[1].pps_id = 0;
-  h264_header.nalus_length = 2;
+  packet_->video_header.h264().nalu_type = H264::NaluType::kStapA;
+  packet_->video_header.h264().nalus[0].type = H264::NaluType::kSps;
+  packet_->video_header.h264().nalus[0].sps_id = 0;
+  packet_->video_header.h264().nalus[0].pps_id = -1;
+  packet_->video_header.h264().nalus[1].type = H264::NaluType::kPps;
+  packet_->video_header.h264().nalus[1].sps_id = 0;
+  packet_->video_header.h264().nalus[1].pps_id = 0;
+  packet_->video_header.h264().nalus_length = 2;
   // Not complete since the marker bit hasn't been received.
   EXPECT_EQ(kIncomplete,
             jitter_buffer_->InsertPacket(*packet_, &retransmitted));
@@ -1202,11 +1200,11 @@
   packet_->markerBit = true;
   packet_->codec = kVideoCodecH264;
   packet_->video_header.codec = kVideoCodecH264;
-  h264_header.nalu_type = H264::NaluType::kIdr;
-  h264_header.nalus[0].type = H264::NaluType::kIdr;
-  h264_header.nalus[0].sps_id = -1;
-  h264_header.nalus[0].pps_id = 0;
-  h264_header.nalus_length = 1;
+  packet_->video_header.h264().nalu_type = H264::NaluType::kIdr;
+  packet_->video_header.h264().nalus[0].type = H264::NaluType::kIdr;
+  packet_->video_header.h264().nalus[0].sps_id = -1;
+  packet_->video_header.h264().nalus[0].pps_id = 0;
+  packet_->video_header.h264().nalus_length = 1;
   // Complete and decodable since the pps and sps are received in the first
   // packet of this frame.
   EXPECT_EQ(kCompleteSession,
@@ -1224,11 +1222,11 @@
   packet_->markerBit = true;
   packet_->codec = kVideoCodecH264;
   packet_->video_header.codec = kVideoCodecH264;
-  h264_header.nalu_type = H264::NaluType::kSlice;
-  h264_header.nalus[0].type = H264::NaluType::kSlice;
-  h264_header.nalus[0].sps_id = -1;
-  h264_header.nalus[0].pps_id = 0;
-  h264_header.nalus_length = 1;
+  packet_->video_header.h264().nalu_type = H264::NaluType::kSlice;
+  packet_->video_header.h264().nalus[0].type = H264::NaluType::kSlice;
+  packet_->video_header.h264().nalus[0].sps_id = -1;
+  packet_->video_header.h264().nalus[0].pps_id = 0;
+  packet_->video_header.h264().nalus_length = 1;
   // Complete and decodable since sps, pps and key frame has been received.
   EXPECT_EQ(kCompleteSession,
             jitter_buffer_->InsertPacket(*packet_, &retransmitted));